Assuming bhaak’s bag of tricks proposal is implemented, allowing an empty bag of tricks to function as a sack:

When the bag is recharged, don’t destroy the contents. Instead, just make the contents inaccessible until it becomes empty again. Also, add a possible random effect to using the bag while charged: it spits out one of its contents at random.

Another proposal is to place the items in the bag into the inventories of the monsters created by the bag. It could even influence which monsters get created (e.g. a monster who will receive an orcish helm from the bag is likely to be an orc).